The present invention relates to a heating and refrigerating machine, especially a Vuilleumier heat pump or a Stirling engine, in which a gas-air mixture is combusted in a combustion chamber and the exhaust gas radiates thermal energy to a heater head, which functions as a housing for the hot piston of the machine, part of the outer surface of the heater head forming a portion of the combustion chamber.
A previously proposed heating and refrigerating machine is described in German Published Patent Application No. 195 16 499 and U.S. Pat No. 5,214,923. In this machine, the gas-air mixture is fed directly into the combustion chamber, ignited and combusted. In the process, the heat transmission is brought about by convection of the exhaust gas on the wall of the combustion chamber and, thus, directly to the heater head. Therefore, only a corresponding efficiency in the energy transmission is achievable.
An object of the present invention is to improve the heat transmission efficiency of a heating and refrigerating machine and, in the process, to achieve a compact design.
This object is achieved, in one case, in that the heater head itself has a concave receptacle functioning as the combustion chamber for a porous-medium burner, the receptacle encompassing the predominant portion of the outer side of the porous-medium burner, with the exception of the intake surface for the gas-air mixture, and in that the heat transmission is brought about by convection and radiation to the heater head, and, in another case, this object is achieved in an equivalent manner in that the heater head is configured as a cylinder and is encompassed by a porous-medium burner in the form of a hollow cylinder, the gas-air mixture being admissible at the end face of the porous-medium burner or at its outer-jacket side, and in that the heat transmission is brought about by convection and radiation to the heater head.
In each case, by using a porous-medium burner, a substantial portion of the heat transmission is brought about by radiation, and by directly coupling the porous-medium burner to the heater head functioning as a part of the combustion chamber, the machine can have a compact structure and can be optimally adapted to space requirements. Moreover, in addition to the improved efficiency of the heat transmission accompanied by low emissions, a large output modulation range is achieved.
One beneficial embodiment of the present invention provides that the porous-medium burner can be arranged at a distance from the heater head or so as to have a large surface area set against the heater head in order to achieve an optimal adjustment with regard to efficiency, removal of emissions, and modulation range.
In this configuration, the porous-medium burner can completely fill the concave receptacle in the heater head.
The combustion of the gas-air mixture in the porous-medium burner can be stabilized in that the gas-air mixture can be fed to the porous-medium burner through a porous anti-blowback body, which covers the intake surface thereof. In this way, a uniform combustion process is achieved inside the porous-medium burner.
The same purpose is also served by an embodiment that is characterized in that a distribution chamber, whose output cross-section corresponds to the input cross-section of the anti-blowback body, is arranged upstream of the anti-blowback body.
The removal of the exhaust gas is ensured, in one case, in that the combustion chamber in the area of the intake surface of the porous-medium body and in the area of the anti-blowback body is covered by a housing having an exhaust outlet, or, in another case, in that the porous-medium burner is covered by a part of a housing having an exhaust gas outlet, the housing part being formed as an anti-blowback body in the area of the intake surface of the porous-medium burner.
A further benefit of the new machine is achieved in that at least one portion of the housing part is formed as a heat exchanger for a circulating liquid, which can be used as water for industrial purposes.